Pond Scum Prized Again
as Potential Biofuel

Few people outside of the
alternative-energy world knew about algae’s renaissance until last July. Exxon
announced that it was plowing $600 million into algae research. The oil giant
entered into a partnership with Synthetic Genomics, headed by Craig Venter, who
pioneered sequencing the human genome in the 1990s. Over the past few years,
Venter and his colleagues have been inserting genes into cyanobacteria to
increase their production of lipids. Exxon expects to have small-scale plants
in operation in five to 10 years.

The Wall Street Journal reacted to the news by declaring that the world had
entered “the summer of algae.” Other companies were getting into the algae game
as well. Solazyme, a corporation based in San Francisco, announced in June that
its funding had reached $76 million. In September it announced that the
Department of Defense had picked Solazyme to supply 20,000 gallons of fuel for
Navy jets. Another company, Sapphire Energy, has $100 million in funding and
promises that by 2011 it will be producing 1 million gallons of diesel and jet
fuel from algae.

Yet these promises do not, in
themselves, guarantee that algae fuel will actu-ally make financial sense.
According to one estimate, it’s still 20 times more expensive to make than
crude oil. And some skeptics don’t believe that the recent flurry of investment
reflects any profound advances in dealing with the great problems associated
with fuel derived from algae.

The best way to get a lot of lipids
out of algae, for example, is to put them under stress. If Scenedesmus
dimorphus is fertilized with a lot of
nitrogen, for example, its cells will end up 20 percent lipids. On a
low-nitrogen diet, that figure rises to 35 percent. Algae probably evolved this
strategy as a way to survive temporary famines. In other words, it’s not
something they can do indefinitely. If you stress algae for too long, says
Peccia, “they’ll just give out.”

In 2008, Peccia, Zimmerman and
Anastas decided to get into the algae fuel game. While corporations were just
tweaking the algae and observing how many lipids they could get out, the Yale
researchers chose a different strategy. “It’s a different way of going about
things,” says Anastas, Teresa and H. John Heinz III Professor in the Practice
of Chemistry for the Environment.

Peccia has been leading the team’s
effort to get to know algae in their most intimate details. “We just want to
understand how they operate, really in the most fundamental way,” says Peccia.
For all the research that has gone into algae, for example, scientists still
know nearly nothing about the genes they use to make lipids. No one has even
sequenced the genomes of any of the lipid-rich microalgae. “We don’t really
know how it all works,” says Peccia.

Because the genomes of microalgae
are so big, Peccia and his colleagues have decided not to sequence all of their
DNA. Instead, they’re just searching for the genes they use to make extra
lipids. To find them, the scientists raise algae in different conditions. For instance,
they rear some of their algae with a lot of nitrogen and some of them with
barely any. The algae respond to these different conditions by switching on
different genes. Peccia and his colleagues then rip open the algae. They fish
out copies of the active genes, called messenger RNAs. From those molecules,
the scientists can determine the sequence of the genes and start to gather
clues about their function.

Peccia and his colleagues are now
mapping out the gene networks that algae use to ramp up their lipid production.
They hope that this knowledge will allow them to precisely manipulate algae
into making more lipids with few side effects. It will then be possible to
abandon the current brute-force methods of starvation.

Even if Peccia and his colleagues
can manipulate algae to become champion lipid makers, however, they will still
face some serious challenges in getting the organisms to thrive outside of a
laboratory flask. The Earth’s waters are loaded with algae, and their diversity
is so vast that scientists are only just starting to catalog it. Some of those
species will inevitably slip into the tanks where engineers rear their designer
algae. “They’re going to have to learn how to compete with these constant
insults of micro-algae coming in,” says Peccia. If they don’t, they’ll get
outcompeted and the tank will become overwhelmed by the wrong kinds of algae.

Peccia has been probing the biology
of algae to look for ways that he can help them win in the real world. He and
his colleagues have found that Scenedesmus dimorphus grows nicely when levels of carbon dioxide are high.
In fact, they keep growing when other species of algae die from carbon dioxide
poisoning. By pumping extra carbon dioxide into algae tanks, engineers may be
able to keep the right species thriving. “If we don’t bubble high CO2 in, the
natural algae outcompete it,” says Peccia.